1. Field of the Invention
The present invention relates to an image processing apparatus such as a color printer that converts, for example, an image signal having red, green, and blue into color information of cyan, magenta, yellow, and black or converts an image signal of an achromatic color into color information of black.
2. Description of the Related Art
A color printer often has two color conversion paths. A first color conversion path uses normal color conversion parameters. The first color conversion path is used when, for example, as print data, an inputted image signal is a chromatic color. The first color conversion path converts, for example, an image signal having red (R), green (G), and blue (B) into, for example, color information corresponding to color materials of the printer, for example, color information of cyan (C), magenta (M), yellow (Y), and black (K).
The first color conversion path holds color conversion data for chromatic colors indicating a relation between an image signal including RGB and color information CMYK represented by color materials. The color conversion data for chromatic colors is stored in a color conversion table for chromatic colors. Therefore, the first color conversion path converts the image signal including RGB into the color information CMYK in accordance with the color conversion table for chromatic colors.
FIG. 7 shows a color conversion result Q1 obtained by the first color conversion path when, for example, an image signal of a character “A” with 50% achromatic colors (R=G=B=50%) is inputted. The color conversion result obtained by the first color conversion path is, for example, C=20%, M=10%, Y=10%, and K=30%. The color conversion result Q1 indicates a ratio for printing the respective colors CMYK with a printer. The printer prints the respective colors CMYK on a print medium such as a print sheet, for example, at a ratio of C=20%, M=10%, Y=10%, and K=30%.
A printing mechanism of the printer usually has some mechanically unstable element. The mechanically unstable element is deviation of print positions of the respective colors CMYK on the print medium. FIG. 8 shows the deviation of the print positions of the respective colors CMYK. Because of the deviation of the print positions of the CMYK colors, in a print result of the character “A”, color bleeding occurs in a contour portion of the character “A” and deterioration in an image quality is caused.
On the other hand, a second color conversion path is used when an inputted image signal is an achromatic color. The second color conversion path converts the inputted image signal into, for example, color information of only a K color of the printer.
The second color conversion path holds color conversion data for achromatic colors indicating a relation between an image signal including achromatic colors and color information of a specific color, i.e., the K color. The color conversion data for achromatic colors is stored in a color conversion table for achromatic colors. Therefore, the second color conversion path converts the image signal of achromatic colors into the color information of only the K color in accordance with the color conversion data for achromatic colors.
FIG. 9 shows a color conversion result Q2 obtained by the second color conversion path when, for example, an image signal of a character “A” with 50% achromatic colors (R=G=B=50%) is inputted. The color conversion result Q2 obtained by the second color conversion path is only the K color. Even if deviation occurs in a print position of the K color because of the mechanically unstable element of the printing mechanism of the printer, in the print result of the character “A”, as shown in FIG. 10, color bleeding does not occur in a contour portion of the character “A” and deterioration in an image quality is not caused.
When an inputted image signal is an achromatic color, the second color conversion path makes it possible to convert the image signal into, for example, color information of only the K color of the printer without deteriorating an image quality. The second color conversion path is effective only when an inputted image signal is an achromatic color. Therefore, the color printer determines whether an inputted image signal is a chromatic color or an achromatic color. When the image signal is a chromatic color, the color printer uses the first color conversion path. When the image signal is an achromatic color, the color printer uses the second color conversion path.
A user requests a favorite hue and brightness with respect to a print result. The user adjusts the color conversion data for chromatic colors in the first color conversion path in order to obtain a print result of the hue and the brightness corresponding to the request. When the color conversion data for chromatic colors in the first color conversion path is adjusted, it is likely that a large difference occurs between the brightness of a color conversion result obtained by the first color conversion path and the brightness of a color conversion result obtained by the second color conversion path.
For example, the color conversion data for chromatic colors in the first color conversion path is adjusted to obtain bright print result. As a result of this adjustment, a print result becomes bright. The color conversion data for chromatic colors in the first color conversion path and the color conversion data for achromatic colors in the second color conversion path are stored in separate tables. Even if the color conversion data for chromatic colors is adjusted, the color conversion data for achromatic colors is not adjusted. The brightness of the color conversion result obtained by the second color conversion path is left intact and is not adjusted. The brightness of the color conversion result obtained by the second color conversion path is lower than the brightness of the color conversion result obtained by the first color conversion path. In the color conversion result obtained by the second color conversion path, compared with the color conversion result obtained by the first color conversion path, gradation jump occurs and causes deterioration in an image quality.
It is necessary to simultaneously adjust the color conversion data for chromatic colors in the first color conversion path and the color conversion data for achromatic colors in the second color conversion path. It is necessary to manage and adjust the color conversion data for chromatic colors and the color conversion data for achromatic color as a pair.
The color conversion data for chromatic colors is represented by an ICC profile. The color printer has an HDD (Hard Disk Drive) built therein. The color conversion data for chromatic colors is often present in a profile stored in the HDD built in the color printer. The color conversion data for achromatic colors is often present as a profile in an independent format.
The color conversion data for chromatic colors and the color conversion data for achromatic colors are selected on the basis of information incidental to an inputted image signal. The incidental information of the image signal is, for example, a difference in a print medium such as a print sheet, a difference in a halftone, and a difference in a print mode. Therefore, a profile is selected on the basis of the incidental information of the image signal. Optimum color conversion data for chromatic colors or color conversion data for achromatic colors is selected from the selected profile. A profile to be selected is determined in advance in association with the incidental information of the image signal such as a difference in a print medium, a difference in a halftone, and a difference in a print mode. Consequently, selection of a profile corresponding to the incidental information of the inputted image signal is accurately performed.
When contents of pieces of incidental information of image signals inputted, respectively, are identical, the color printer selects an identical profile every time the image signal is inputted. For example, color conversion data for chromatic colors in the profile is adjusted to a hue and brightness corresponding to a request of the user. The adjustment of the color conversion data for chromatic colors in the profile cannot be specified only from a file name. Therefore, it is impossible to determine, with only the file name, what kind of color conversion data for chromatic color the color conversion data for chromatic colors is. To discriminate content of the profile, it is necessary to select the profile and take trouble to print the profile on a print medium. In some cases, it is difficult to distinguish delicate differences in a hue, brightness, and the like on the basis of a print result on the print medium. The print result on the print medium is also different depending on a state of the color printer.
JP-A-2003-110857 discloses that, when print conditions of a print system are changed, a print profile used for color conversion is easily updated. The publication discloses that, when update registration of a print profile is performed by a personal computer of a printing company, a print profile downloaded to a personal computer of a design and production company by a profile management server is automatically updated.